.TH std::print 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::print \- std::print

.SH Synopsis
   Defined in header <print>
   template< class... Args >                                      \fB(1)\fP (since C++23)
   void print( std::format_string<Args...> fmt, Args&&... args );
   template< class... Args >

   void print( std::FILE* stream,                                 \fB(2)\fP (since C++23)

               std::format_string<Args...> fmt, Args&&... args );

   Format args according to the format string fmt, and print the result to an output
   stream.

   1) Equivalent to std::print(stdout, fmt, std::forward<Args>(args)...).
   2) If the ordinary literal encoding is UTF-8, equivalent to
   (std::enable_nonlocking_formatter_optimization<std::remove_cvref_t<Args>> && ...)
       ? std::vprint_unicode_locking(stream, fmt.str, make_format_args(args...))
       : std::vprint_unicode(stream, fmt.str, make_format_args(args...));.
   Otherwise, equivalent to
   (std::enable_nonlocking_formatter_optimization<std::remove_cvref_t<Args>> && ...)
       ? std::vprint_nonunicode_locking(stream, fmt.str, make_format_args(args...))
       : std::vprint_nonunicode(stream, fmt.str, make_format_args(args...));.

   The behavior is undefined if std::formatter<Ti, char> does not meet the
   BasicFormatter requirements for any Ti in Args (as required by
   std::make_format_args).

.SH Parameters

   stream  - output file stream to write to

             an object that represents the format string. The format string consists of
               * ordinary characters (except { and }), which are copied unchanged to
                 the output,
               * escape sequences {{ and }}, which are replaced with { and }
                 respectively in the output, and
               * replacement fields.

             Each replacement field has the following format:

             { arg-id (optional) }               \fB(1)\fP
             { arg-id (optional) : format-spec } \fB(2)\fP

             1) replacement field without a format specification
             2) replacement field with a format specification

                           specifies the index of the argument in args whose value is
                           to be used for formatting; if it is omitted, the arguments
                           are used in order.
             arg-id      -
                           The arg-id s in a format string must all be present or all
                           be omitted. Mixing manual and automatic indexing is an
                           error.
   fmt     -               the format specification defined by the std::formatter
             format-spec - specialization for the corresponding argument. Cannot start
                           with }.

               * For basic types and standard string types, the format specification is
                 interpreted as standard format specification.
               * For chrono types, the format specification is interpreted as chrono
                 format specification.

               * For range types, the format specification is interpreted
                 as range format specification.
               * For std::pair and std::tuple, the format specification
                 is interpreted as tuple format specification.
               * For std::thread::id and std::stacktrace_entry, see       (since C++23)
                 thread id format specification and stacktrace entry
                 format specification.
               * For std::basic_stacktrace, no format specifier is
                 allowed.

               * For std::filesystem::path, see path format               (since C++26)
                 specification.

               * For other formattable types, the format specification is determined by
                 user-defined formatter specializations.
   args... - arguments to be formatted

.SH Exceptions

     * std::bad_alloc on allocation failure.
     * std::system_error, if writing to the stream fails.
     * Propagates any exception thrown by used formatters, e.g. std::format_error.

.SH Notes

   Feature-test macro  Value    Std                 Feature
                      202207L (C++23) Formatted output
   __cpp_lib_print    202403L (C++26) Formatted output with stream locking
                              (DR23)
   __cpp_lib_format   202207L (C++23) Exposing std::basic_format_string

.SH Example


// Run this code

 #include <cstdio>
 #include <filesystem>
 #include <print>

 int main()
 {
     std::print("{0} {2}{1}!\\n", "Hello", 23, "C++"); // overload (2)

     const auto tmp {std::filesystem::temp_directory_path() / "test.txt"};

     if (std::FILE* stream{std::fopen(tmp.c_str(), "w")})
     {
         std::print(stream, "File: {}", tmp.string()); // overload (1)
         std::fclose(stream);
     }
 }

.SH Output:

 Hello C++23!

.SH See also

   println             same as std::print except that each print is terminated by
   (C++23)             additional new line
                       \fI(function template)\fP
   print(std::ostream) outputs formatted representation of the arguments
   (C++23)             \fI(function template)\fP
   format              stores formatted representation of the arguments in a new string
   (C++20)             \fI(function template)\fP
   format_to           writes out formatted representation of its arguments through an
   (C++20)             output iterator
                       \fI(function template)\fP
   printf
   fprintf             prints formatted output to stdout, a file stream or a buffer
   sprintf             \fI(function)\fP
   snprintf
   \fI(C++11)\fP
